This invention relates to a conveyor truck having improved running characteristics.
A conventional conveyor truck of the same general type to which the invention pertains is shown in FIGS. 1 and 2. FIG. 1 is a bottom view of the conventional conveyor truck and FIG. 2 is a plan view of the same. Reference numerals 1 and 2 designate a truck body and wheels, respectively; 3, blocks for supporting rotary shafts of the wheels 2; 4 and 5, a motor and a power transmission mechanism, respectively, for imparting power to the wheels 2; 6, auxiliary wheels secured to the truck body 1; and 7, a load-supporting bed.
In operation, rotational movement of the two motors 4 is imparted by the power transmission mechanism to the wheels 2 for causing movement of the truck body 1. During the running of the truck, the auxiliary wheels 6 serve to support the truck body 1 without interfering with the running thereof.
The modes in which the truck can be run may be classified into two groups. One is a rectilinear running mode in which the truck is advanced and retracted along the same straight line as that in which the truck is oriented. The other mode is a curvilinear running mode including curve running and turning about a fixed point in which the truck is run about a point on an extension of the axis of rotation of the two wheels 2. FIG. 3 shows the manner in which the truck is rectilinearly run, whereas FIGS. 4 and 5 illustrate the manner in which the truck is curvilinearly run, wherein arrows indicate the direction in which the truck is advanced.
Rectilinear running of the truck is obtained by driving the two motors 4 via the power transmission mechanism 5 to synchronously rotate the two wheels at the same speed and in the same direction. On the other hand, the curvilinear running of the truck is attained by controlling the rotational speeds of the two motors 4 in such a manner that the ratios of the distances between the centers of curvature of the running loci of the two wheels to the rotational speeds of the two wheels is maintained at a specified value.
According to the conventional conveyor truck constructed as aforementioned, a complicated sequence of combinations of rectilinear and curvilinear runnings is required, for instance, if it is desired to move the truck along spaced parallel lines. This involves certain disadvantages since the orientation of the truck must be changed a plurality of times, making subsequent alignment of the truck with the original orientation impossible. Also, a wide space is required for movement of the truck.